Preparation of synthetic hydrocarbon lubricating compositions

ABSTRACT

SYNTHETIC HYDROCARBON LUBRICATING COMPOSITIONS, SUCH AS THOSE DISCLOSED IN U.S.PAT. 3,598,739, HAVING IMPROVED POUR POINT PROPERTIES MAY BE PREPARED IN SITU BY FRIEDELCRAFTS ALKYLATION OF A MIXTURE OF MONOALKYL-SUBSTITUTED AROMATIC COMPOUNDS CONTAINING AT LEAST 2 VOLUME PERCENT OF TETRAHYDRONAPHTHALENE COMPOUNDS WITH A HALOGENATION PRODUCT DERIVED FROM PARTIALLY CHLORINATING OR BROMINATING PARAFFINS.

United States Patent 3,775,325 PREPARATION OF SYNTHETIC HYDROCARBON LUBRICATING COMPOSITIONS Oliver C. Kerfoot and Delmar D. Krehbiel, Ponca City, Okla., and George C. Feighner, Franklin Lakes, NJ., assignors to Continental Oil Company, Ponca City, Okla. No Drawing. Filed May 30, 1972, Ser. No. 258,137 Int. Cl. Cm 1/16 US. Cl. 25259 12 Claims ABSTRACT OF THE DISCLOSURE Synthetic hydrocarbon lubricating compositions, such as those disclosed in US. Pat. 3,598,739, having improved pour point properties may be prepared in situ by Friedel- Crafts alkylation of a mixture of monoalkyl-substituted aromatic compounds containing at least 2 volume percent of tetrahydronaphthalene compounds with a halogenation product derived from partially chlorinating or brominating DISCLOSURE This invention relates to an improved method for preparing synthetic hydrocarbon lubricating compositions comprising mixtures of alkyl-substituted aromatic compounds and higher alkyl-substituted tetrahydronaphthalene compounds.

Heretofore, various synthetic lubricants have been developed to improve upon petroleum-derived lubricants. For example, US. Pat. 3,173,965 discloses dialkylbenzenes having properties rendering them useful as lubricants while US. Pat. 3,288,176 discloses a bottoms fraction derived from the condensation of a substantially straight chain paraflinic hydrocarbon with an aromatic hydrocarbon as being useful as a lubricant. Among the advantages of synthetic lubricants, in general, are improved viscosity and your point properties.

Recently, it has been found that the pour point properties of dialkylbenzenes can be improved by incorporating therein additional quantities of higher alkyl-substituted tetrahydronaphthalenes, preferably higher trialkyl-substituted tetrahydronaphthalenes, as indicated in US. Pat. 3,598,739 to Sias. Such compositions, according to Sias, are formed by separately preparing the higher alkyl-substituted tetrahydronaphthalenes and then physically blending them with the previously prepared dialkylbenzenes sufficient to bring the total content of higher alkyl-substituted tetrahydronaphthalenes in the blend to a level whereby the improved pour point properties are achieved. Thus, while the composition blends have highly desirable properties, the technique by which they are formed sufiers from the disadvantage of requiring separate preparation of the higher alkyl-substituted tetrahydronaphthalenes which can be blended with the dialkylbenzenes to attain necessary levels of the tetrahydronaphthalene derivatives in the final composition blend.

In accordance with this invention, it has unexpectedly been found that compositions of the general type disclosed in Sias may be prepared in situ without the necessity for separately forming an additional quantity of higher alkylsubstituted tetrahydronaphthalenes and then blending it with the dialkylbenzenes. In general, the invention involves the discovery that when a mixture of monoalkylsubstituted aromatic compounds containing a quantity of tetrahydronaphthalene compounds is alkylated with a halogenation product derived from partial halogenation of parafiins, a compositions is obtained containing polyalkylsubstituted aromatic compounds and higher alkyl-substituted tetrahydronaphthalene compounds but wherein the quantity of higher alkyl-substituted tetrahydronaphthalene compounds formed is substantially increased. Thus, with wherein Ar is benzene, toluene, or xylene; R is, independently, an alkyl group having 6 to 24 carbon atoms; and n is an integer of 2 or 3;

and at least 10 percent by volume, based on the polyalkyl-substituted aromatic compounds, of higher alkylsubstituted tetrahydronaphthalene compounds of the formula wherein A is, independently, an alkyl group having 1 to 20 carbon atoms provided that when more than one A substituent is present the sum of carbon atoms for all A substituents is 2 to 20; y is 0 or an integer of 1-4; R is independently, H or an alkyl group having 1 to 22 carbon atoms provided that the sum of carbon atoms for both R substituents is 5 to 23; and x is an integer of 1-3.

In the above-described polyalkyl-substituted aromatic compounds, it is preferred that Ar is benzene; each R, independently, is a straight or branch chain C -C alkyl group, preferably C C and n is equal to 2.

In the above-described higher alkyl-substituted tetrahydronaphthalene compounds, it is preferred that each A, independently, is a straight or branch chain alkyl group having 1 to 13 carbon atoms provided that when both A substituents are alkyl groups the sum of carbon atoms is 6 to 14; y is equal to 2; each R is, independently, H or a straight or branch chain alkyl group having 1 to 18 carbon atoms, preferably 1 to 16 carbon atoms, with the sum of both R substituents being 7 to 19 carbon atoms, preferably 9 to 17; and x is equal to 1.

It has been found in accordance with the method of this invention that the above compositions may be prepared in a single step alkylation reaction as described hereinafter.

The material to be alkylated in forming compositions as described above is a mixture of monoalkyl-substituted aromatic compounds of the formula ArR and at least 2 percent by volume, based 0 nthe monoalkyl-substituted aromatic compounds, of tetrahydronaphthalene compounds of the formula Ar, R, A and y are, in their broad and preferred forms,

as defined above in connection with the polyalkylsubstituted aromatic compounds and the higher alkylsubstituted tetrahydronaphthalene compounds, respectively.

For convenience in describing the invention hereinafter, the above-described polyalkyland monoalkyl-substituted aromatic compounds will be referred to as FAA and MAA, respectively, and in their preferred forms when Ar is benzene and n is 2 they will be referred to as DAB and MAB, respectively. Similarly, the above-described higher alkyl-substituted tetrahydronaphthalene compounds and reactant tetrahydronaphthalene compounds in their broad sense will be referred to as HATHN and THN, respectively, and in their preferred forms wherein y is 2 and x is 1, they will be referred to as TI I-IN and DTHN, respectively.

As indicated above the mixture to be alkylated in accordance with the method of this invention comprises MAA containing at least 2 percent by weight, based on the MAA, of THN. It has unexpectedly been found that when such a mixture is alkylated as hereinafter described the resulting product composition contains at least percent by volume, based on PAA, of HATHN. In general, it may be said that when the mixture being alkylated contains of the order of 20 volume percent THN, based on MAA, the resulting product composition will contain in excess of about 50 volume percent HATHN, based on PAA. It is contemplated that the mixtures being alkylated contain from about 2 volume percent up to about 30 volume percent THN, based on MAA, although it should be understood that greater amounts may be included and the upper limit of 30 volume percent does not form an essential feature of the invention. On the other hand, it is essential that the mixture contain at least about 2 volume percent of THN in order that the product composition contains sufiicient HATHN to obtain the advantages discussed in the aforemenioned Sias patent. For most product compositions intended for lubricant utility, the mixture being alkylated should preferably contain about 2 volume percent to volume percent THN.

The MAA may be obtained by simple alkylation of an aromatic compound such as benzene, toluene or xylene, with an olefin or a chlorinated paraffin having the appropriate carbon content as is well-known in the art; for example, see the techniques described in U.S. 3,173,965. A particularly suitable technique for preparing MAA is also described in U.S. 3,316,294 wherein chlorinated paraffins are employed. In this latter process, some THN is also produced along with the MAA and thus provides a convenient source for the mixture to be alkylated in this invention, at least insofar as lesser quantities of THN may be required in the material to be alkylated. On the other hand, THN may be obtained by careful fractionation of the product prepared by the process described in U.S. 3,316,294 and thereafter added to the MAA in any proportion desired depending upon the mixture desired for the alkylation.

The halogenation product used to alkylate the mixture of MAA and THN may be derived by partially chlorinating or brominating C C parafiins to the extent whereby from about 10 to 35 mol percent of the paraffiris become halogenated. The degree of halogenation should not exceed about 35 mol percent so as to attain satisfactory selectivity to the monohalogenaed derivaives. On the other hand, the halogenation should exceed about 10 mol percent for practical reasons. While both bromine and chlorine may be employed as the halogenating agents, it is preferred to use chlorine due to its ready availability. Conventional halogenation techniques may be employed including both liquid or vapor phase conditions. A highly suitable halogenation technique which may be used to obtain suitable halogenation products useful in the method of this invention is described in U.S. 3,316,294, it being understood that the technique described therein is applicable with both branched and straight chain parafiins having 6 to 24 carbon atoms. Preferably, the halogenation product is derived from straight chain parafiins having 8 to 20 carbon atoms, more preferably 10 to 18 carbon atoms. It is also pointed out that the partially halogenated reaction mixture may be employed as such in the method of this invention as the unreacted paraifins will merely be carried through the process as inert materials. Alternatively, the halogenated parafiins may be separated from the unreacted paraffins thus avoiding accommodation of the inerts in the process.

The alkylation reaction is preferably conducted as a Friedel-Crafts reaction using a suitably inorganic halide Friedel-Crafts catalyst such as AlCl AlBr FeCl SnCl BF BC1 ZnCl HF, H P 0 H PO antimony chlorides, and mercuric chlorides. Preferably, the Friedel- Crafts catalyst is aluminum chloride or aluminum bromide with the most preferred catalyst being aluminum chloride.

The reaction may be carried out at temperatures in the range of about 20 to 0., preferably 50 to 90 C., using a molar ratio of MAA to the halogenated parafiin in the range of about 1:1 to about 10:1, preferably about 2:1 up to about 6: 1. The quantity of catalyst which may be used may range from about 1 to about 10 percent by weight, based on the halogenated paraffin, preferably about 3 percent to about 8 percent by weight.

The alkylation reaction can be carried out in a continuous or batch-wise manner for a period of time sufiicient to complete the alkylation as in well-known in the art. Thereafter, the reaction product efiluent can be introduced into a separator whereupon a product phase and catalyst sludge phase are formed. The catalyst sludge phase may be easily decanted off and either removed from the process or recycled back to the alkylation reaction. The product phase may then be treated to remove any acidic components by any conventional technique such as treating with sulfonic acid and washing with a caustic solution or percolation through a bauxite bed. After any such preliminary treatment, the product phase may be fract'mnally distilled to remove any unwanted lower boiling materials as desired.

The following examples are presented for the purposes of further illustrating the above-described method of this invention:

EXAMPLE 1 To a creased three-necked stirred flask, there were added 540 g of a mixture of linear tridecylbenzene (C MAB) containing 3.4 volume percent C tetrahydronapthalenes (DTHN) and g. of chlorinated C normal paraffin, and the flask was heated to about 65 C. The chlorinated C normal parafiin was obtained by chlorinating a quantity of C normal paraflin to the extent of about 20 mol percent in accordance with the technique described in U.S. Pat. 3,316,294 followed by separation by distillation of any unreacted normal paraflin.

The C tetrahydronapthalenes were obtained in admixture With tridecylbenzene by alkylating benzene with a partially chlorinated C parafiin also described in U.S. Pat. 3,316,294. Six g. of AlCl catalyst were then added and the mixture stirred for about 1 /2 hours while maintaining the temperature at about 65 C. The reaction mixture was then gravity settled into the two phases, an upper product phase and a lower catalyst sludge layer. The lower catalyst sludge layer (about 18 g.) was then removed while the remaining upper product phase was washed with dilute aqueous caustic and distilled to remove the lower boiling unreacted materials with the cut being taken at 220 C. a 10 millimeters Hg. The resulting 219 g. of product, by mass spectrometer analysis, comprises C dialkylbenzene (DAB) containing about 14 volume percent higher alkyl tetrahydronapthalenes ('ITHN).

EXAMPLE 2 For comparison, the procedure set forth in Example 1 was repeated except that the starting tridecylbenzene (C MAB) contained no C tetrahydronapthalenes (DTHN) as taught in the prior art. The resulting dialkylbenzene product amounted to 170 g. of which mass spectrometer analysis indicated that only 3 volume percent of higher alkyl tetrahydronapthalenes (TTHN) were present.

EXAMPLE 3 In a further example of the method of this invention, 1400 g. of a mixture of MAB (C -C monoalkylbenzenes) containing 6.4 volume percent DTHN (C -C tetrahydronapthalenes), 1170 g. of partially chlorinated C -C normal paraffins were charged to a creased threenecked stirred flask and heated to about 70 C. The mixture of MAB and DTHN was prepared in accordance with the technique described in US. Pat. 3,316,294. The partially chlorinated parafiins were prepared as described in the same patent, the extent of chlorination being approximately mol percent. 18 AlCl catalyst were then added to the flask and the reaction mixture was stirred at 70 C. for about 1% hours. The reaction mixture was then gravity settled into two phases and the lower catalyst sludge layer (about .58 g.) was removed. The remaining product mixture was washed with a dilute aqueous caustic solution and distilled to remove the lower boiling unreacted materials with the cut point being taken at 225 C. and 10 millimeters Hg. The DAB product mixture amounting to about 484 g. was found to contain, by mass spectrometer analysis, 78 volume percent dialkylbenzenes (DAB) and 19.2 volume percent higher alkyl tetrahydronapthalenes (TTHN). In addition, the unreacted MAB fraction recovered from the distillation step was found by mass spectrometer analysis to contain 5.8 volume percent of the DTHN.

The DAB product mixture possessed very attractive low temperature physical properties as outlined in Table l hereinafter.

EXAMPLE 4 In a further example demonstrating the method of this invention, the unreacted MAB fraction recovered from the distillation step in Example 3 was subjected to alkylation as follows: 850 g. of the recovered MAB fraction containing 5.8 volume percent of O -C tetrahydronaphthalenes (DTHN) was charged to a three-necked stirred flask along with 527 g. of partially chlorinated C -C normal paraffins as described in Example 3, and the mixture was heated to about 70 C. Seven g. of AlCl catalyst were then added to the tflask and the reaction mixture was stirred for about 1% hours at 70 C. Thereafter, the reaction mixture was gravity settled into two phases at the lower catalyst sludge layer, amounting to about 28 g. was removed. The remaining product mixture was then washed with a dilute aqueous caustic solution and distilled to remove the lower boiling unreacted materials with the cut point being taken at 225 C. and 10 millimeters Hg. The resulting dialkylbenzene (DAB) product mixture amounted to about 236 g. and contained by mass spectrometer analysis about 23 volume percent higher alkyl tetrahydronaphthalenes (TTHN). The product again exhibited good low temperature physical properties which are outlined in the following table.

Thus, having described the invention in detail, it will be understood by those skilled in the art that certain modifications and variations may be made in the invention without departing from the spirit and scope thereof as defined herein and in the appended claims.

We claim:

1. A method of preparing a synthetic hydrocarbon lubricating composition comprising polyalkyl-substituted aromatic compounds of the formula wherein Ar is benzene, toluene, or xylene; R is, independently, an alkyl group having 6 to 24 carbon atoms; and n is an integer of 2 or 3;

and at least 10% by weight, based on the polyalkyl-substituted aromatic compounds, or higher alkyl-substituted tetrahydronapthalene compounds of the formula are which method comprises alkylating a mixture containing monoalkyl-substituted aromatic compounds of the formula Ar(R), both Ar and R being as defined above, and at least 2% by weight, based on the monoalkyl aromatic compounds, of tetrahydronapthalene compounds having the formula both A and y being as defined above, in a Friedel Crafts reaction with a halogenation product derived from partially chlorinating or brominating C to C parafins to the extent whereby from about 10 to 35 mol percent of the paraflins are halogenated.

2. A method according to claim 1 wherein the mixture being alkylated contains about 2 volume percent to 30 volume percent of said tetrahydronapthalene compounds.

3. A method according to claim 1 wherein in the monoalkyl-substituted aromatic compounds, Ar is benzene and R is a straight or branched chain C -C alkyl group.

4. A method according to claim 3 wherein R is a straight or branched chain C C alkyl group.

5. A method according to claim 3 wherein R is a straight chain alkyl group.

6. A method according to claim 3 wherein in tetrahydronapthalene compounds, A is a straight or branched chain alkyl group having 1 to 13 carbon atoms and y is equal to 2.

7. A method according to claim 6 wherein the alkyl group represented by A is straight chain.

8. A method according to claim 6 wherein the mixture being alkylated contains about 2 volume percent to about 15 volume percent of said tetrahydronapthalene compounds.

9. A method according to claim 1 wherein the alkylation is carried out at temperatures in the range of about 20 to C. in the presence of a Friedel-Crafts catalyst.

10. A method according to claim 9 wherein the halogenation product is derived from partially chlorinating (l -C paraffins.

11. A method according to claim 10 wherein the molar ratio of monoalkyl-substituted aromatic compounds to halogenated paraflins is in the range of about 1:1 to about 10:1.

12. A method according to claim 9 wherein the quantity of catalyst used is in the range of about 1 to 10 weight percent based on the halogenated paraflins.

References Cited UNITED STATES PATENTS 3,538,178 11/1970 Sias 25259 X 3,662,012 5/ 1972 Feighner et al 260672 T 3,458,447 7/1969 Shultz 260671 BX 8 3,391,210 7/1968 Feighner et a1. 260671 BX 3,598,739 8/1971 Sias 26059 3,661,780 5/1972 Feighner et a1. 26059 DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner US. Cl. X.R. 260671 B 

